Endocardial mapping catheters have heretofore been provided. See, for example, U.S. Pat. No. 5,156,151 to Imran. Movable electrodes have been provided for use therewith. U.S. Pat. No. 5,400,783 to Pomerariz et al., for example, discloses a plurality of movable electrodes mounted on an arm swingably disposed within a basket assembly. U.S. Pat. No. 5,324,284 discloses an endocardial mapping system utilizing a separately controlled ablation catheter. See also U.S. Pat. No. 5,476,495 to Kordis et al. It has been found that endocardial mapping catheters having other types of movable electrodes would be desirable.